Method of making pressure vessles and the like



Feb. 17, 1942. Q RAYMOND ET AL 2,273,735

METHOD OF MAKING PRESSURE VESSELS 'AND THE LIKE Filed Deo. 5, 1938 3sheets-sheet 1 Lig. 1.

N INVENTORS wynn@ Rayma/m Mer/ Q Cr'eec, am(

lfd/p: Fea 5.

ATTORNEY Feb. 17, 1942. Q RAYMOND ET AL 2,273,736

METHOD OF MAKING PRESSURE VESSELS AND THE LIKE Filed Dec. 5, 1938 5Sheets-Sheet 2 INVENTORS Gwyn/1e Hay/wond, Mcr/ D. Creer/7, and

' 6 L, Fea /est f-zTTQlmQEY Feb. 17,1942. @RAYMOND ETA., 2,273,736

METHOD OF MAKING PRESSURE VESSELS AND THE LIKE Filed Deo. 5, 1958 3Sheets-Sheet 3 I NVENTO R S Gwynne Rayma/:

Mer/ D. reet/1, am! E Fra Mm Patented Feb. 17, 1942 t UNITED STATESPATENT oFFlCE METHOD F MAKING PRESSURE VESSELS AND THE LIKE GwynneRaymond, Meri D. Creech, and Ralph L. Feagles, Oklahoma City, Okla.-Application December 5, 1938, Serial No. 244,076

2 Claims. (Cl. 22S-148.2)

This invention relates to a method of manu- Fig. 1 to better illustratethe attachment of a facturing pressure vessels and the like,particufitting in the Wall thereOf.

larly vessel capable of withstanding extremely Fig. 4 is a perspectiveview of the inner shell high working pressures and temperatures. orfoundation of a vessel, having the heads Industry of today requiresvesselswhich are 5 Welded thereto and showing the method of testadaptedto safely contain high pressures and ing for leaks, Particularly thewelds securing the temperatures. In fact, many high pressure heads t0the shell. processes require the use of vessels in such size Fig. 5 is adetail perspective View illustrating that the walls must be as much assix to eight the method of winding a continuous metal ribinches inthickne'ss. The manufacture of such 1o bon 0n the tested shell. wherebyany predetervessels is difficult and an extremely expensive mined degree0f tension may be DrOduCed in the procedure. Where plates of thisthickness are respective layers aCeOrding t0 the WOrking Dresused,forging and heat treatment must be re- SuleS With Which the tank 1S t0be subjected. sorted to as it is impractical to roll metal sheets Fig- 6is a fragmentary Section 0f the Wall 0f of the required thickness.Themeta1 also be- 1B the tank in the course of construction.particucomes s0 greatly distorted 0r deformed in the laIly illustratingthe method 0f Welding the 1ammanufacturing procedure that the internalina/tions. stresses seriously weaken the vessel and it is Fig- 7 is adetail perspective View O'f a .iOint dliicult to calculate the safeworking pressures used in fOrIning a ribben 0f sufeient length t0 thatthey may withstand, To solve these probprovide the required number ofwrappingslems attempts have been made to form vessels Fig. 8 is a.detail fragmentary seCtiOn 0f a by winding layer upon layer of sheetmetal to rnOdied form 0f Vessel.

build up walls of the desired thickness, and then Referring more indetail t0 the drawings:

to form the layers in as nearly a homogeneous In carrying Out Ourinvention. We have dismass as possible by heating and forging, but, thecovered that when pressure is applied within the result is inaccurateand unsafe vessels result. interior 0f a thiCk Walled Vessel tending toen- It is, therefore, the principm purpose of the large the innerdiameter thereof, the outer dipresent invention to provide a method offorming ameter is not increased pereeptibly. This is ac laminatedvessels wherein the internal stresses COllnted fOr in the fatt that theinner portion 01 y cf the weu structure may be sc ccntrcued that thewall has compressed and the Outer portion wherein: s

a vessel may be relied upon to safely contain 0f the Wall iS Placed intenSOn. With the result the working pressures for which it, was designedthat the internal stresses seriously weaken the other objects or theinvention are tc'provide vessel and it is not Capable of safelyretaining a method of forming a laminated vessel having a the WOrkingpressures fOr which the Wall thickhigh strength weight ratio for `safelycontaining ness Was designed. We have also discovered a given pressure;to provide a method of vessel that this Same aCtOn takes Place in alaminated construction by which the vesse1 may be accu- Wall with theresult that the stresses imparted rately tested for leaks; and toprovide a method in the VafQnS layers d0 n0t adequately Perform offorming laminated vessels wherein the lamithen Part 1n Wlthstandmg hlghinternal Pres' nations are securely anchored to the heads of 40 Eures'We have thelfefoe' found it essential. to the vessel and each layertakes its part of the lkelolf'ent?? lsb'lrganlg Working Stresses whenthe vessel is placed in so that the tension is controlled am? varid)aeg: operation' Q cording to the stresses which the respective lay- Inaccompllshing these and other obJects of ers must Withstandto form avessel of maximum the invention, as hereinafter pointed out, we

strength for a given number of laminations and have prov1ded an improvedmethod of procedure, wan thickness as illustrated in the accompanyingdrawings, When the cylindrical wan cfa vessel is formed merely bywinding one convolution on another Fig. 1 is a longitudinal sectionthrough a ves- 50 and the heads welded thereto, it is diilicult to selconstructed in accordance with the present prevent leaks, and when aleak does occur the method. pressure creeps out between the laminationsso Fig. 2 is a. cross-section through the vessel on that its origincannot be determined from the the line 2 2 of Fig, 1. y outside of thevessel. To overcome this difficulty Fig. 3 is a similar section on theline 3-3 of 55 we have adopted the principle of the automobile tirewherein an inner tube prevents leaks and the outer easing gives therequired strength. We therefore make up an inner shell I by rolling asheet of material of a desired thickness to withstand testing pressures,taking in consideration the inner diameter of the tank, the materialbeing sufiieiently thin to permit ready fabrication thereof incylindrical form, and weld to the ends thereof heads 2 and 3 which arepreferably formed of solid metal and of desired thickness to withstandthe internal working pressures of the completed vessel.

In the illustrated instance the heads 2 and l are substantiallyhemispherical in form and have their inner radius corresponding to theinner radius of the shell, the outer radius corresponding to the outerdiameter of the finished tank, ns shown in Fig. l. The abutting faces Itherefore project eireumferentially of the outer surface of the shelland are tapered from the plane of the centers of curvature to facilitatewelding. as later described. The heads 2 and 3 are placed concentricallywith the axis of the shell I and are welded, as indicated at 5 and l.

If the shell of the tank is to be provided with a fitting 1, the fittingshould be of proper thickness to withstand the internal pressures of thefinished vessel. In the illustrated instance the iitting i is in theform of a ring. having a central opening 8 registering with acorresponding opening 9 in the shell. The outer periphery of the fittingis rounded on suitable curves, as at III, and the terminal thereofflattened, as at l l, to temporarily secure a closure plate I2. The faceof the fitting secured to the shell is countersunk, as at I3, to receivewelding I4, by which the fitting is attached to the shell. The portionof the fitting encircling the weld is preferably tapered, as at I5, toform an annular space to receive a welding material IB, supplementingthe inner weld Il. The plate I2 is secured over the opening 3 by boltsI1 extending therethrough and secured in threaded sockets in theflattened face of the fitting. The plate I2 carries a T- fitting IB, oneterminal of which is connected by a nipple I3 with a central opening inthe plate, and the other connections are respectively provided with aliquid supply line and a pressure gauge 2i whereby liquid is admittedinto the tank under pressure, as indicated by the gauge 2I, to test theshell or foundation against leaks prior to completion of the vessel, asnow described.

After testing, the plate I2 is removed. and suitable trunnions 22 and 23are temporarily welded or otherwise attached to the heads 2 and 3 in theaxis thereof, as shown in Fig. 5, whereby the shell is rotatablysupported in bearings 2l and 23 secured to suitable supports 23 and 21.One of the trunnions, for example 22, is of sufficient length to beconnected with any suitable power for effecting rotation of the shell. Ametal ribbon is then prepared, having a width corresponding to thespacing between the heads of the tank, and of sufficient length toprovide the necessary number of convolutions to produce a tank of apredetermined wall thickness. One end of the ribbon is then skived andwelded to the shell of the tank by -a transverse weld, as shown in Fig.5. The ribbon is then placed in a gripping device, such as clamping bars28 and 2l having angle shaped inner faces 30 and 3i cooperating withwedge plates 32 and 33 directly engaging the upper and lower surfaces ofthe ribbon. The wedge plates are drawn into clamping engagement with theribbon by drawbolts Il and 35, inserted through the ends of the clampingbars 28 and 29. The thicker portion of the wedges are arranged so thatwhen pulling pressure is applied to the bars in a direction away fromthe welded end of the ribbon, this pressure acts to enhance grippingaction of the wedges so as to prevent slippage between the bars andribbon. The ends of the bars are suitably connected with hydrauliccylinders 3B and 31, through rods 3B `and 3B, whereby variable tensionsmay be -applied in the ribbon through control of the fluid pressuremedium used in the respective cylinders. the pressures being indicatedby gauges IU and 4I connected with the respective cylinders.

While tension is being maintained on the ribbon, the foundation is beingrotated to wrap the ribbon about the shell I. On each revolution it isnecessary to out an opening l2 in the ribbon so that the fitting willpass therethrough, permitting the convolutions to closely engage eachother whereby fric-tional contact of one convolution on the otherprevents unwinding thereof and therefore maintains the imparted tension.If desired the ribbon may be provided with welding apertures I3, wherebyone convolution is welded to the other, as indicated at M. A sufiicientnumber o1' convolutions is wound on the shell so that the peripheralface of the final convolution registers with the peripheral edges of theheads. During readjustment of the bars 2B and 2li,` when the hydraulicmechanisms have come to the end of their stroke, tension may bemaintained on the ribbon by a similar mechanism, adjustable weights, orthe like. When the winding is complete, the free edge of the ribbon maybe skived, as indicated at 45, and welded to the underlying convolutionby welding 4B.

In order tov provide a welding space between the ends of theconvolutions and the heads, the side edges of the ribbon are so shapedthat when wound on the shell they will lie on an angle corresponding tothe angle of the head faces to form a welding space in which a weldingmaterial is deposited, as indicated at 4i and I8. Welding material isalso filled in around the fitting, as indicated at 49. The trunnions arethen removed from their supporting bars and cut from the ends of theheads, completing the tank assembly.

In tanks requiring longer ribbons than the length of sheets obtainable,they may be formed of a series of sheets preferably having the ends cuton a bias, as shown at 50, Fig. 7, whereby the joint'extencls spirallyrelatively to the shell so that the gripping action of the upper andlower sheets supplements the strength of the weld.

In extremely long tanks. two or more ribbons may be wound on the shelland welded together in the same manner as above described.

In order to avoid skiving or featherlng of the inner edge of the sheet,or that edge attached to the shell I, the edges of the shell, whensecured together, may be offset as indicated at 5I in Fig. 8. The edge32 of the ribbon may then be abutted against the offset and welded asshown.

In Order to give a better understanding of the variable or differentialtension applied in the respective convolutions to produce a tank ofmaximum strength, the following is a calculation for a vessel having a Ainch shell rolled to 14 inches inside diameter, then wound with a 1;/8inch plate to bring the nal outside diameter to 171/2 inches giving atotal wall thickness of 1% inches, a working pressure within the tankassumed to be 3,000 pounds per square inch:

The A. S. M. E. Code gives the following as the stress in the abovevessel:

Stress: 15.75 X 3000/2 X 1.75: 13,500 1b./Sq. in.

The stress in the above vessel using the more exact equation derived andapplicable to shells relatively thick compared to the diameter (Strengthof Materials Case, Longmans, Chap. XXVIII) 3000 X49 76.5 +49 S-m m4913,680 1115./111.2

Stress at outer radius where r=r2 has been reduced to 453 pounds and thetension in the second convolution 538 pounds. 'I'hus the tensions of theconvolutions, after the final one has been applied, are the ilgures atthe bottoms of the columns. It will be noted that these ngures are forpractical purposes of similar rela-'- tive magnitude, for example thetension in the first convolution is now 288 pounds and the tension inthe outermost convolution 300 pounds.

From the foregoing calculations it is seen that the stress is notdistributed uniformly throughout the thickness of the shell but isgreatest at the inner surface. 'I'he difference between the inner andouter fibre stress Will become more and more as the thickness of theshell is in-v creased with respect to the diameter.

By varying the tension in the laminations any desired stressdistribution may be obtained. Thus, by suitably varying the tension inthe lamnations, unequal distribution of stresses is overcome.

Tensions and compressions in the different layers as they are Wound onthe vessel:

The headings in the above tables designate the thickness of the shelland the convolutions wound therearound. It will be noted that theconvolutions are eight in number. The figures in column one designatecompression forces on the inner shell which vary from 600 pounds withthe nrst convolution to 2443 pounds after the eighth convolution hasbeen applied. The iirst figures in the following columns designatetension in pounds per inch of Width maintained in the ribbon as theconvolutions are formed. The subsequent figures in these columns definethe tension maintained in the convolutions with each wrap. For example,vafter the second convolution has been wound over the first maintaininga tension of 600 poun"ds per inch of Width in the second convolution,the tension of the first convolution has been reduced from 600 to 515pounds. After the third convolution has been formed, the tension in thefirst convolution Attention is also directed to the fact that as eachconvolution is wound upon a succeeding convolution, the tensions of thesucceeding convolutions are reduced in progressive order. Since thevessel is in equilibrium, the algebraic sum of all the tensions andcompressions in any horizontal line of the above table will be zero.

The stresses due to the above tensions and to the internal pressure willbe as follows:

. Initial Stress due Total Radlus stress to pressure stress The abovetable designates stresses. The first column designates the radius of therespective convolutions. The second column denotes the initial stress onthe respective convolutions due to the winding tension, and the thirdcolumn designates stress when internal pressure is applied in the tankif the convolutions were wound with zero tension. The final columndenotes the total stress. Column two is obtained by dividing thetensions in the last line of the ilrst table by the thickness ofthevarious convolutions. Column three is calculated by applying theabove equation, and the iigures in the last column are obtained byadding the gures in columns two and three.

In the above tabulation, the total stress is the algebraic sum of theinitial stress and the stress due to the internal pressure.

The above calculations for a specific tank are merely illustrative ofthe variable stresses imparted in the respective layers, and thesestresses may be varied therefrom to provide a tank suitable for anygiven service.

From the foregoing it is apparent thatvwe have provided a method ofproducing a laminated tank wherein the respective convolutions aremaintained under a predetermined initial stress calculated to givemaximum strength and to safely withstand the working pressures for whicha tank is designed.

What We claim and desire to secure by Letters Patent is:

1. The method of -making a laminated vessel capable of withstanding ahigh predetermined internal pressure including forming a tubular shell,applying a fitting to the shell, testing the tubular shell for leaks,Winding a sheet metal ribbon into a plurality of convolutions about theshell one directly upon another with the surfaces of one convolution infrictional contact with those of adjacent convolutions whereby saidfrictional contact maintains the convolutions from relative movement,forming openings in the respective convolutions at the time of windingto pass the ntting, applying differential tension in the respectiveconvolutions at the time and place ot said winding, and welding theconvolutions to said shell.

2. The method oi making a laminated vessel capable o! withstanding ahigh predetermined internal pressure including iorminz a tubular shell.applying a iltting to the shell, testing the tubular shell for leaks.lwinding a sheet metal ribbon into a plurality of convoiutions about theshell one directly upon another with the surfaces of one convolution infrictional contact with those o! adjacent convolutions whereby saidfrictional contact maintains the convolutions from relative movement,forming openings in the respectlvc convolutions at the time o! windingto pass the iittin. applying tension in the respective convolutions atthe time and place oi said winding, and welding the convolutions to saidshell.

GWYNNE RAYMOND.

MERL D. CREECH.

RALPH L. FEAGLEB.

